A vehicle body has wheel assemblies, each of which includes a vehicle wheel and a tire attached to the wheel. Each wheel assembly is provided with a tire condition detecting apparatus, which detects the condition of the tire such as the air pressure and the temperature in the tire. Each tire condition detecting apparatus has a function of transmitting a signal indicating the detected tire condition. When the receiver mounted on the vehicle receives signals from the tire condition detecting apparatuses, a display displays the conditions of the respective tires based on the signals. Since each tire condition detecting apparatus is attached to a wheel assembly, the apparatus incorporates a battery to supply power.
For example, Patent Document 1 discloses a tire condition detecting apparatus that has a function of identifying the rotational position of a wheel assembly at a predetermined interval and transmits a signal corresponding to the rotational position of the wheel assembly. The vehicle has angle sensors provided at positions corresponding to the wheel assemblies to detect the rotational positions (the rotational angular positions) of the wheel assemblies. When the receiver receives signals transmitted from the tire condition detecting apparatuses, the rotational positions of the wheel assemblies obtained from the signals are checked against the rotational positions detected by the angle sensors. This allows each condition detecting apparatus, which is the source of a signal, to be identified as the one provided in a specific wheel assembly.